OS/DP would win for me. OS for the pacing, we were pretty much through most of the gyms, the characters were developing well. Ash had obtained some fairly decent pokemon with good personalities.
DP takes the win though, I adore the first season of DP, those first 50 were gold! Ash and Dawn were a good way into their quests, Dawn's development arc started where her first struggles in contests were beginning. Ash, Brock and Dawn had some great pokemon. I loved the interactions of the pokemon, Pikachu, Aipom, Staravia, Turtwig, Piplup, Buneary, Pachirisu, Buizel, Sudowoodo, Croagunk and Happiny were a good cast. They were getting good treatment in terms of the trainers pokemon. Plus Cacnea had a good release.
And the rivals were developing nicely, both Paul and Zoey, plus we'd been introduced to some other rivals, Nando and Kenny for example.
And we were just about to begin the Hearthome Tag Battle too.
The pacing was great.
I don't understand why XY is so high up......especially the first part of the series was pretty lackluster, Serena had not long captured his second pokemon. Had she even competed in her first showcase? Had anything notable happened other than captures?